2022-2025 Audi A3/S3/RS 3 Headlight Warning DTC B126A29

Symptoms

Owners of 2022-2025 Audi A3, S3, and RS 3 vehicles may notice an intermittent warning light for the exterior lighting or adaptive light displayed in the instrument cluster. Despite this warning, the lighting system continues to function normally without any issues. This condition is specifically addressed by Audi Technical Service Bulletin 2073612/1.

Fault Codes / DTCs

When diagnosing this issue, technicians may find one or more of the following Diagnostic Trouble Codes (DTCs) stored in the Onboard Supply Control Unit (J519, address word 0009):

DTC	Description
B126A29	Light switch range/performance
U112100	Databus missing message
U110B00	Light switch no communication

Diagnosis / Trigger Conditions

The root cause of the intermittent headlight warning and associated DTCs, including the Audi S3 headlight warning B126A29, is identified as overly sensitive diagnostics within the J519 control unit. This sensitivity leads to false warnings being triggered.

It is important to note that if only DTC U110B00, labeled as "Light switch no communication," is stored, the cause might be a loose pin or wire. In such cases, this specific Technical Service Bulletin 2073612/1 does not apply, and normal diagnostic procedures should be followed.

Important Warnings for Owners

Audi advises that no repairs are currently necessary for this condition. Owners should not replace any components for this issue, as doing so will not resolve the underlying concern. A temporary measure to clear the warning lamp is to press the "AUTO" button on the light switch, which will reset the fault detection.

Repair Procedure Summary

Audi is actively working on a permanent solution for the overly sensitive diagnostics in the J519 control unit. This solution is expected to be available by the end of the 4th quarter of 2024, though this timeline is subject to change. Until then, dealers are instructed to explain the situation to customers and to create a Pending Service Solutions (PSS) record in their system. No physical repairs or component replacements are to be performed at this time for the Audi S3 headlight warning B126A29.

Warranty Information

This Technical Service Bulletin (TSB) applies to vehicles covered under Audi's New Vehicle Limited Warranty, which typically extends up to 48 months or 50,000 miles, whichever comes first. For Certified Pre-Owned (CPO) vehicles, the claim type is G10. If the vehicle is outside of warranty coverage, this bulletin serves as informational guidance only.

Labor Operations

For warranty claims related to this issue, the following labor operations and codes are specified:

• Service Number: 9405
• Damage Code: 0040
• Labor Operations:
  • Service light switch (9405 4199): Maximum 50 Technical Units (TU)
  • Diagnostic Time (GFF 0150 0010): Refer to SRT for associated operations
  • Diagnostic Time (GFF 0150 0060): Time stated on diagnostic protocol (Maximum 50 TU)
  • Road test prior to service procedure: No allowance (0 TU)
  • Road test after service procedure: No allowance (0 TU)

NHTSA ID: 10253293 ```